The present invention is to provide a microfluidic device capable of allowing a fluid to stably flow in a microchannel without using an external source such as a pump or a suction device, and the microfluidic device, provided with a microchannel to which a sample liquid is transported, includes: an inlet reservoir which reserves a sample liquid to be introduced into said microchannel; an inlet which is provided on a sample-introduced side of the microchannel, and communicates with the inlet reservoir; an outlet provided on a sample-discharged side of the microchannel; and an open channel which is provided as communicating with the outlet, and part of at least one surface of which is opened to the outside atmosphere, wherein the inlet is provided at a higher position in a gravity direction than the outlet.